City researchers to study technology of cannons
Neha Madaan, TNN Jun 19, 2011, 08.14pm IST
PUNE: Researchers at the city-based Government College of Engineering, Pune (CoEP) and the Deccan College Post-Graduate and Research Institute have initiated a project to catalogue 250 cannons in as many as 100 forts of Western Maharashtra. The project will also include metallurgical and technical analysis reports of these cannons.
The researchers have found that among these 250 cannons, five massive ones were made by forge welding. This corroborates the fact that the process was indigenously developed, not borrowed from Europe.
The research also found three cannons in cast and forge-welded condition, obtained from a procedure earlier not known to have existed during that time.
Forge welding is a solid-state welding process that joins two pieces of metal by heating them and then hammering them together.
It was also found that the atmospheric corrosion resistance of the Kalal Bangadi cannon in Janjira, marine fort, was excellent and can be compared with the iron pillar in Delhi.
Under the ongoing project, funded by the Indian National Science Academy, New Delhi, and the University Grants Commission, the researchers have also created 2D drawings and 3D models of the cannons studied, so that they could be replicated later, as only half of their original number remains today.
Sachin Joshi, a researcher from Deccan College, and P P Deshpande from the department of metallurgy and materials science, CoEP, assisted by Shivendra B Kadgaonkar, an archaeology student, undertook the documentation and analysis of the cannons.
"There are very few technical analysis reports on forge welded cannon technology in the country. Western Maharashtra is dotted with a number of forts, all housing forge welded cannons, which have not been documented and studied. The project offers an insight into the present condition and state of the metallurgical monuments, apart from providing a basis for further technical investigations," said Deshpande.
Joshi said there were a large number of cannons in the forts earlier. "We now see only half of this number, as a lot of these cannons were destroyed by those who visit the forts. People often throw cannons off fort tops, collect the metal pieces and sell them. Thus, we are documenting what remains, so that even if some cannons are destroyed, they could later be reproduced," said Joshi, adding that they have also marked the position of these cannons through GPS, in order to track a cannon if it is displaced.
The metallurgical and technical studies, undertaken by Deshpande include analysing the composition, metallography as well as rust analysis. "It shed light on the possible manufacturing technology used in those times," he said.
Joshi and Kadgaonkar visited the forts to take measurements and photograph the cannons. "Essays written by 19th century trekkers speak at length about the number of cannons. However, only half of these have remained. There are forts that were believed to have cannons, but we found none during our visits."
According to Joshi, out of the original 30, only 18 cannons remain in the Rasalgarh fort. "Approximately, 6 out of a total of 25 cannons remain in Sinhagad, while 65 out of 200 remain in Janjira fort."
Neha Madaan | tnn
Pune: The cannons are the testimony of the engineering expertise of medieval India. According to P P Deshpande of CoEP, there are at least 50 cannons at the Janjira fort even today. "Of these, three are forge welded iron cannons - the Kalal Bangadi, the Chavari and the Landa Kasam. It is certain that these massive cannons were not cast. This means they were made of wrought iron. There is no specific recorded history. However, it is said that the largest cannon, Kalal Bangadi, 5.4 m in length and 14 tons in weight, was brought by the Peshwe's army in 1735. It was a muzzle-loading type, where gun powder and projectile objects are loaded from the muzzle, i.e., the front end," Deshpande said.
He said the outer appearance of the cannon indicates that individual pre-fabricated iron rings were forge welded in order to create the complete cannon structure. "The rings exhibit good continuity. The skill of the medieval blacksmith must be appreciated as these rings have been so skillfully forge welded that the entire surface appears smooth. It also appears that medieval engineers were familiar with the idea of structural design for improved fracture toughness," he said.
Another remarkable aspect of the cannon is that it is almost devoid of significant rusting. "The surface possesses a reddish golden hue and it is reflective, indicating the relatively thin layer present on the surface. This may be attributed to the high phosphorus present in the wrought iron used in the cannon. It, however, must be noted that no special maintenance procedures are currently applied to this cannon," said Deshpande.
Despite the neglect, the cannon reveals only pitting corrosion. "Under similar marine environment, modern mild steel would have corroded severely. Thus, the atmospheric corrosion resistance of the cannon is excellent," said Deshpande.
Sachin Joshi, from the Deccan College, said that the three cannons documented were made using both the processes-casting and forging. "It was not known that the medieval Indian blacksmith's skill in design engineering and construction had reached this level of finesse even then. A cannon in Sinhagad fort, another called Bhavani Prasad in fort Mulher in Nashik and yet another in Devgiri fort in Aurangabad, are examples of such cannons," said Joshi.